1. Field of the Invention
The present invention relates to an edge detection apparatus, an image forming apparatus, and an edge detecting method.
2. Description of the Related Art
In electrophotographic image forming apparatuses, there is conventionally known a technology to detect an end portion (which is referred to as “an edge” in the following description) in a width direction of a transfer sheet. An edge position of the transfer sheet is detected by, for example, an optical detection unit, such as a contact image sensor (which is referred to as “CIS” is the following descriptions) placed in a conveying path of the transfer sheet (for example, Japanese Patent No. 4794979 etc.). Based on the detected edge position of the transfer sheet, a shift amount of a document in the width direction (which is referred to as “main-scanning direction” in the following descriptions) is calculated so as to adjust a transfer position on the basis of the transfer sheet or to adjust the position of the transfer sheet on the basis of the transfer position for achieving correction in the main-scanning direction for each transfer sheet. Moreover, a skew amount is calculated on the basis of the detected edge of the transfer sheet. These technologies have already been known, and in the case of detecting the edge of the transfer sheet by using these technologies, an influence of paper powder generated during conveyance of the transfer sheet needs to be eliminated. For this, a technology to perform dust removal processing is known.
Moreover, for high-speed transfer of data (data for edge detection) read with, for example, a CIS, a technology to divide and send out the data read by the CIS is also known.
However, according to an edge detection method disclosed in, for example, Japanese Patent No. 4794979, when the data read by the CIS is divided and sent out, continuous output of an output value indicative of the presence of a transfer sheet is interrupted at boundaries of divided CIS data. This makes it impossible to perform accurate edge detection.
In view of the above-stated circumstances, there is a need to provide an edge detection apparatus, an image forming apparatus, and an edge detecting method, capable of performing accurate edge detection even when data for edge detection is divided and sent out.